The present invention relates to an automatic dispensing machine capable of dispensing elongated flexible coiled elements such as wire from heavy spools or buckets in which the wire is wound about a central axis. This invention controls the unwinding of the elongated flexible element from a spool, drum, or loose coils particularly wherein the element is to be dispensed at high rates and intermittent and sporatic feed requirements. Typical uses of this type of automatic wire dispensers are for automatic welding machines or wire forming machines such as for springs and the like. In these types of industrial operations for welding operations or forming of springs, the feed requirements are sometimes drastically demanding of high rates of wire feed and intermittent and sporadic feed.
As related above, wire is generally wound on a spool, within a drum or is a loose coil. In all of these forms, the wire is wound in a coil shape about a central axis. Further, a wire spool, drum or loose coils generally contain a large quantity of wire; for example, a single wire spool, drum or loose coils can weigh up to as high as or more than 1000 lbs. Large coils of this size create problems because the weight requires a substantial force to start the coil rotating and when it once starts rotating the inertia force of the coil is high causing the problem of the coil wanting to continue rotating. Thus, in the start of the winding of the wire from a coil, some means has to be provided to rotate the coil at precisely the right time and speed and once the spool or drum starts rotating a brake means is generally required to slow down the rotation of the coil.
Failure to control the start up and the stopping of the coil and the speed of the coil in between creates quite some problems, particularly when it is desired to have a high speed of wire removal at certain times, lower speed at other times and/or intermittent and sporadic stopping and starting. An improper control has a deleterious effect upon the wire being dispensed by either stretching the wire or fouling up the wire when the rate it is being dispensed is too fast.
Still another problem with the use of large supply coils is that as the wire is withdrawn from the coil, the weight of the coil diminishes, resulting in a change in the inertia force that affects the starting and stopping and the variable dispensing requirements.
Extended efforts have been made by those skilled in the art to produce an automatic wire dispensing machine that solves all of the problems set forth above. Most of the attempts in controlling the dispensing of wire have employed a motor means on which the coil is located. The motor rotates the coil as the wire is being dispensed. The problem has been how to control the actuation and speed of the motor and also the inertia of the coil. Many attempts have been made to control the speed and the starting and stopping by a braking means. Some provide tension control devices that are intended to match the feed rate with the demand rate. Other machines have provided slack wire loops that permit the machine using the wire to make rapid and intermittent use of the wire while providing the wire feed at a more continuous rate. All of these machines are quite complicated, require adjustments to accommodate different sizes of wire, spools and drums and have unsuitable limitations on the rate the wire can be dispensed and the kind of wire.
One wire dispensing machine which has proven successful for certain rates of dispensing and for certain weights of spools and drums is disclosed in my patent application Ser. No. 189,422 filed on May 2, 1988, and entitled AUTOMATIC WIRE DISPENSER (now U.S. Pat. No. 4,899,945). The machine described in such patent application includes a wire guide mounted for oscillating movement in response to changes in wire tension, and has a drive and control system which in response to the position of the wire guide progressively increases and decreases the rate of rotation of the spool to pay out the wire faster in response to an increase in wire tension and at a decreased rate on reduction of wire tension. Although the wire dispenser in the above said patent application works satisfactorily for many uses, the control mechanism involves a number of pulleys which are more complicated than desired and it cannot handle dispensing of wire at desired higher rates, particularly at high speed stops and starts.
The object of the present invention is to provide an improved automatic motorized dispenser that is simple in construction, simple to operate, inexpensive and accommodates wide ranges of operating conditions, particularly at higher rates of dispensing than has been accomplished by previous automatic dispensers.